Reluctantly, and with horrific images of Hillsborough too easily brought to mind, football was forced yesterday to confront the possibility of a return to fences in the wake of the latest outbreak of serious hooliganism.

Both the Football Association and Chelsea, immediately launched investigations into the pitch invasion and brawling between rival supporters immediately after the FA Cup replay with Millwall at Stamford Bridge. The west London club admitted that if fans continue encroaching on to the field the barriers might have to go back.

Another woeful Wednesday, the third for a beleaguered game in succession, saw 38 arrests and 19 fans charged. Eleven police officers were injured as the fighting spilled into neighbouring streets. Missiles were thrown and tear gas used. "Officers came under completely unprovoked and extreme violence at points during the evening," a police spokesman said.

Dave Mitchell, the Millwall striker, was knocked over and spat at and his team-mate, Ben Thatcher, hit on the back of the head as fans spilled over the barriers after Millwall completed their penalty shoot-out victory.

Coming only a week after a Blackburn supporter invaded the Ewood Park pitch to attack the referee, and a fortnight after Eric Cantona's attack on a fan, the shameful scenes provided more ammunition for those who say the game is running out of control.

Within minutes of the Stamford Bridge violence erupting, the FA was in touch with its crowd control observer at the game. Talks continued through the night and yesterday the authorities began collating reports into the most serious outbreak of crowd disorder this season. At the same time Chelsea, who face the possibility of censure and a heavy fine, if found to be at fault, announced they were taking urgent measures to identify, and ban, the troublemakers.

In a statement issued on behalf of the club, the managing director, Colin Hutchinson, deplored , "as do 99 per cent of our supporters" the incidents and the repercussions that could ensue. "Football spectators, by consistently good behaviour, had perimeter fences removed. Sadly there is a danger of the actions of a few bringing these back."

It was in fact the appalling loss of life at Hillsborough that brought the fences down and the police gave a cool response last night to talk of their return. "There are arguments for and against," a spokesman said, "but safety considerations and the fear of a repeat tragedy, would, I am certain, outweigh other concerns."

David Davies, the FA's director of public affairs, said: "We have to look at all the possibilities but if you believe what happened to be an isolated incident the balance of probability would be against a return to fences."

After disturbances in the first game between the sides, the police had mounted the largest security operation seen at a London match game in recent times. There were 30 mounted officers in a force totalling 400 and in addition hundreds of stewards were involved.

"The police, well supported by stewards, suppressed problems inside the stadium," said Hutchinson, "and we thank the police and our own staff for their speedy response to the charged atmosphere at the end of the game.

"We are saddened that a few spectators - and we stress a few - have tarnished Chelsea and football. We don't want them at Stamford Bridge and we appeal to all the 99 per cent of genuine fans who attended the match to give us, in confidence, any written information they can to speed up identifying those involved.

"We will be studying in minute detail the closed-circuit television video tapes to identify the culprits. We will institute exclusion orders on those traced. We would expect Millwall to act likewise with any of their identifiable followers. We would hopethe ringleaders will be prosecuted and convicted with tough sentences."

The North Stand, the ground's newest, was hailed in Wednesday's match programme as "the start of something special" by the club's chairman, Ken Bates, who once wanted to install an electrical fence to restrain fans. He also wrote: "Bad behaviour is a curse. Stewards are paid to stop this. If they do nothing, tell us. Better still, since the good guys greatly outnumber the bad, do your own neighbourhood watch operation."

Unhappily, recent events confirm the view that hooliganism has not been eradicated from the game, merely contained. "We have made great strides in dealing with hooligans in recent years and I hope we are not going back to the days when they seemed to dominate the game," said the FA chief executive, Graham Kelly.

His authority would again examine ways to make it hard for spectators to cause trouble. "A full investigation is underway," said the FA's spokesman Mike Parry. "We are determined to find the root cause and do all in our power to prevent a repeat. It was a totally unacceptable situation."

n Police would like anyone with information about the disturbance to phone the Hooligan Hotline on 0800 515495.